One of my professors, a solid priest but by no means a traditionalist, made an interesting point about the communion fast. The one-hour fast as it is in the current practice of Latin Catholics is pretty negligible; for Sunday Mass all one really has to do is make sure not to eat or drink in church or on the way.
When the fast was longer, either the three hours prescribed by Pius XII or from midnight before that, it could account for those who did not receive Holy Communion. In other words, if someone didn't receive, one might presume that he or she had not kept the fast for whatever reason. Nowadays, offered my professor, there is only one reason for someone to abstain from Holy Communion after having been previously admitted to the sacrament: the state of serious sin.
Thus, he opined, reinstating a longer communion fast could be a great pastoral kindness by providing (as it once did) a pretext for abstaining from Holy Communion for those who were actually unable to receive due to struggles with serious sin or other habitual troubles in their state of life, and thereby give them the dignity of some privacy.